This invention relates to a wrench which is reversible to drive a socket in either direction while rotating freely in the opposite direction, and in particular to such a wrench which is driven through frictional engagement of rollers.
Clutch mechanisms utilizing frictional engagement of a plurality of rollers have long been used as the drive element of reversible wrenches in order to achieve essentially instantaneous engagement. Heretofore, such wrenches have had several shortcomings which have prevented their use from becoming wide spread in the market despite the inherent advantages they have over rachet-type wrenches.
Prior art wrenches of this type generally fall into two categories. Wrenches in the first category utilize one set of rollers for driving the wrench in the clockwise direction and another set for driving it in the counter-clockwise direction. This type of wrench is typified by Pratt, U.S. Pat. No. 2,469,572, and, due to the duplication of drive rollers, is expensive to fabricate. The other category of wrenches of this type, which includes the wrench of the present invention, uses the same rollers for both clockwise and counterclockwise rotation.
In order to achieve a good bite of the rollers, the prior art single-driving roller wrenches generally have arcuate cam faces such as those shown in Kounousky, U.S. Pat. No. 1,904,621, Freber, U.S. Pat. No. 2,119,622, and Richardson, U.S. Pat. No. 338,780. Where planer cam faces have been utilized, such as in Brown, U.S. Pat. No. 2,584,256, it has been in a four-roller system, which, due to its symmetry, has a tendency to become cocked.
In addition the prior art detents used to lock the wrenches in either their clockwise or counterclockwise direction of rotation have been in or out type of devices. Thus if the selector is not fully positioned, the wrench will not become engaged properly and slipage will occur.